This invention relates to the field of fiber optics, and more particularly to a cassette for storing varying lengths of excess optical fiber during the installation of optical fiber cable.
There are many applications that utilize an optical fiber network to establish optical communications between a host digital terminal (HDT) at a central office and an optical network unit (ONU) at a remote location. Typically, each ONU installation will have a unique optical fiber cable routing. Each strand of optical fiber cable follows a different path between the HDT and the ONU, and will have an excess length of optical fiber that must be stored.
The optical fiber cable consists of the optical fiber and two electrically conducting tension wires. The optical fiber itself is extremely fine, on the order of 0.25 mm (0.0098 inches) in diameter. In order that the optical fiber not become kinked, which will degrade the quality of light pulses traveling through it, the optical fiber must not be bent sharply anywhere along its path. The two tension wires accompanying the optical fiber are referred to as tension lines, as they provide mechanical resistance to stretching when the optical fiber cable is under tension. Since optical fiber cable, and in turn the tension lines, may be subject to lightening strikes, the tension lines must be grounded at tie-down points.
The joining together of two fibers end-to-end to carry a signal of light pulses is called a splice connection. The splice connection must be held in place securely.
As cutting optical fibers is a delicate process, special tools and small jigs are used to perform the whole cleaving operation. For most applications, the ends are cut close to perpendicular to the optical fiber axis. Cleanly cleaved optical fiber ends are needed for low loss fusion splices. For high-performance optical connectors and mechanical splices, the cut tip of the fiber is ground and polished. Cables that are field installed are often terminated before installation to approximately the length needed, resulting in an excess length of optical fiber that must be stored.
In accordance with the present invention, there is provided an optical fiber cassette, for use in connection with an optical domain network to store excess optical fiber cable. The optical fiber cable includes an optical fiber and a tension wire. The optical fiber cassette comprises a chassis having at least one spool for winding and storing excess optical fiber, the spool having a wall with a radius of at least a minimum bend radius.
A method is also disclosed.